Using Software Defined Network (SDN) technology, various complex network applications can be implemented through software programming in a control panel, for example, EPS/GPRS is implemented by SDN. Specifically, an Evolved Packet System (EPS) network is the 4th generation mobile communication network defined by the 3rd Generation Partnership Project (3GPP), and a General Packet Radio Service (GPRS) network is the 3rd generation mobile communication network defined by the 3GPP.
The architecture of an EPS network implemented through an SDN is shown in FIG. 1, where UE is a communication terminal. An Evolved Universal Terrestrial Radio Access Network (EUTRAN) is a radio access network, the inside of which is made up of an evolved Node B (eNB). A core network part, i.e., Evolved Packet Core (EPC, a core network part of EPS) network defined by software, is composed of a Mobility Management Entity (MME), a Serving Gateway (SGW), a Packet Data Network Gateway (PGW) and other device. Each unified Gateway (UGW) is a general gateway device, whose role is controlled by control signaling of an SDN controller (simply referred to as controller). In the figure, both the SGW and the PGW are played, by a UGW in which they are positioned, according to the indication of the controller. For these gateway roles, it is not excluded that two or three gateway roles are taken by a same UGW, if they are taken by a same UGW, an interface between network elements becomes an internal interface.
The architecture for a GPRS system implemented by an SDN to be accessed to an EPS network is shown in FIG. 2, where UE is a communication terminal. A Universal Terrestrial Radio Access Network (UTRAN) is a radio access network, whose inside is made up of an eNB and a Radio Network Controller (RNC). The core network part is also a core network part, EPC, of EPS, however, a function of the mobile management is performed by a control plane function of S4-SGSN (Serving GPRS Support Node) of an SGSN, i.e., by an SGSN supporting S4 interface (S4-SGSN). The SGW is an SGW supporting for interfacing with S12 of the RNC. The PGW is the same as the PGW of FIG. 1. Both the SGW and the PGW are controlled by the UGW of the controller.
The problem which occurs to the implementation of an EPS/GPRS network by an SDN is explained below referring to FIG. 1. In a traditional EPS system, a control plane and a user plane of an SGW are integrated; the SGW is selected by an MME according to positioning information, subscription information and the like of UE. However, in a system implemented by the SDN, a control plane and a user plane of the SGW are separated, the control plane of the SGW is implemented actually by a controller while the function of the user plane of the SGW is implemented by a Unified Gateway (UGW) according to an instruction from the controller to perform. Therefore, the MME is only able to select a controller, which UGW is selected to perform function of the user plane of the SGW depends on the controller. Thus each UGW is located in a pool, or in a management domain, and each UGW is borne by a general switch device or a virtual switch, thus current load information of the UGW and ON state information of the virtual switch are required to be considered in addition to the positioning information, subscription information and the like of the UE, when the controller selects a UGW. Thus, in the EPS/GPRS network implemented by an SDN, a scenario may occur, i.e., the UGW is reselected not due to the changes of positioning information, subscription information and the like of the UE but due to the change of the load state of the UGW or the ON state of the data center virtual machine, thereby the user plane of the SGW is relocated, and address of the user plane of the SGW is changed.
In a traditional internet, whether the SGW is changed is decided and perceived by the MME, the MME can actively initiate an operation for repositioning the SGW, thereby solving the forwarding problem of the user data flow and ensuring continuity of a service and integrity of the data. However, in the EPS/GPRS system implemented by the SDN, since change of the SGW cannot be perceived by the MME/S4-SGSN, a front-end network element cannot acquire information of a new SGW when the SOW has been changed, which may result in problems of disconnection of the link in the user plane, and the disconnection of the user service and disruption of the user data. When the controller reselects a POW, the case may occur that the user plane information of the new POW cannot be acquired by the MME, thereby leading to subsequent handover operation error, and thus leading to the disruption of user data.
Therefore, in a scenarios of an EPS/GPRS network implemented by an SDN, there arises a problem always that a front-end network element cannot acquire information of a new gateway when a gateway is reselected by the controller, which may result in the disconnection of the user service and disruption of the user data.